Chip amp power supply- a beginners guide - Page 56 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 3rd August 2010, 02:38 PM   #551
diyAudio Member
 
Join Date: Jun 2010
Hi !
I have a question regarding a power supply kit bought on eBay.
Components on the board : 10000uF NOVER capacitors, 0.1uF WIMA capacitors, 4.7K resistors, 35A rectifier bridge.

Click the image to open in full size. Click the image to open in full size. Click the image to open in full size.

I have a toroidal transformer with dual 24v secondaries ( 4 wires ) ... as you can see in the pictures above there are 3 "pins" for the input labeled AC-GND-AC. How should I connect the wires from the transformer ? . It's part of a LM3886 Kit.

Last edited by mvandrei; 3rd August 2010 at 02:43 PM.
  Reply With Quote
Old 3rd August 2010, 02:50 PM   #552
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
build a mains light bulb tester.
Use it to power up the transformer.
It will help stop you injuring yourself and help avoid destruction of your transformer/project.
you need to join two of the secondary wires.
From this junction you run a wire to the central GND pad.
The other two secondaries go to the AC pads.
Do this wrong and you risk an accident.
Do take precautions to avoid damage.
__________________
regards Andrew T.

Last edited by AndrewT; 3rd August 2010 at 03:13 PM.
  Reply With Quote
Old 12th August 2010, 06:54 PM   #553
lgreen is offline lgreen  United States
diyAudio Member
 
lgreen's Avatar
 
Join Date: May 2003
Location: San Diego, USA
Nuuk- the regulated power supply links on your website page having to do with power supplies are not working. Pedja took his pages down.

this one- http://www.pedjarogic.com/gc/supplies.htm and the related ones.
__________________
Retired from DIY (2010) but still lurking now and again. My DIY audio projects- PartTimeProjects.com.
  Reply With Quote
Old 12th August 2010, 07:10 PM   #554
diyAudio Member
 
Tripmaster's Avatar
 
Join Date: Feb 2008
Location: UK
Quote:
Originally Posted by lgreen View Post
Nuuk- the regulated power supply links on your website page having to do with power supplies are not working. Pedja took his pages down.

this one- http://www.pedjarogic.com/gc/supplies.htm and the related ones.
Did you mean this page?

Pedja Rogic Audio Pages - Chip Based Power Amp i.e. Gainclone - Regulated Supplies
__________________
Richard
My photostream: http://www.flickr.com/photos/59839778@N04/
  Reply With Quote
Old 12th August 2010, 08:27 PM   #555
lgreen is offline lgreen  United States
diyAudio Member
 
lgreen's Avatar
 
Join Date: May 2003
Location: San Diego, USA
Nuuk's page-
Building a Gainclone chip amp power supply.

has this paragraph-
I wasn't too keen on the LM338 regulated GC but I love (and still use) the discrete regulated version designed by Pedja Rogic. If you would like to try the >>discrete regulated power supply<< but don't have the confidence to build your own on stripboard, the good news is that you can now buy either PCB's, or completed modules from Pedja. See >>here<< for details.

the links are broken.
first link
http://www.pedjarogic.com/gc/supplies.htm

2nd link
http://www.audialonline.com/diy/moduler/

probably the same as the one you link to? Anyway, the links are dead and I wanted to tell Nuuk about it.
__________________
Retired from DIY (2010) but still lurking now and again. My DIY audio projects- PartTimeProjects.com.
  Reply With Quote
Old 12th August 2010, 09:10 PM   #556
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Sorry, I forgot that link was still there. Unfortunately (but perhaps understandably) Pedja has dropped all his DIY stuff to concentrate on his commercial sales. He did let me know but I forgot that I had that link still on the site.

I have now updated the site but please be aware that I am only updating the 'new' site these day. So that page is now at:

Building a Gainclone chip amp power supply.

Please bookmark the new URL.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 13th August 2010, 03:22 AM   #557
niacinj is offline niacinj  United States
diyAudio Member
 
Join Date: Aug 2010
Default Bi-amping 5 channels with 10 GC amps

Hello,
Just a few questions if anyone has suggestions or starting points, as I am new to designing my own amplifiers. My goal is to bi-amp 5 separate MTM speakers that I just finished building for a total of 10 amplifiers. I will be using the LM3886 chip. The crossover frequency is 2.5kHz. The woofers are 8 ohm 88dB 35 watts each and the tweeters are 6 ohm 92dB 40 watts each.
First question - Would there be any benefit to run the woofers in series for 16ohm load instead of parallel to 4ohms? Obviously there would be less overall output power, less current through the chip, but the damping should improve. Does anyone know the appropriate power supply voltage for this impedance?
Second question - Since I am bi-amping, effectively using two amplifiers in place of one, would the two amps require the same power as one amplifying the full range? Can I obtain more power from each amp with the narrower bandwidth?
Lastly, question three - Any ideas for the size of the power transformer for such a system? If I do go with a higher DC voltage for running the woofers at 16ohm, should I use separate transformers for high and low frequency? I plan on using separate supply boards for each amp as it is.
I did do research, but not many people have created a ten channel GC.
I appreciate any and all help!
  Reply With Quote
Old 13th August 2010, 10:33 AM   #558
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
if you want to power multiple amplifiers in a single box then it is far easier if all can run from the same voltage.

Can your drivers be set to the same sensitivity?

I think they can (maybe).

Design for +-28Vdc from a 22+22Vac transformer. This can power a chip whether it's connected to a 4ohm, or 6ohm, or 8ohm, or 4 to 8ohm speaker.

The drivers are:
Quote:
The woofers are 8 ohm 88dB 35 watts each and the tweeters are 6 ohm 92dB 40 watts each.
Two woofers in parallel from one chipamp present a 4ohm load.
The resulting sensitivity is 88dB/2.83V @ 1m + ~6dB = ~94dB/2.83V @ 1m. Well quite a bit less because the amplifier cannot double it's power when the load is reduced from 8ohm to 4ohm. Subtract between 0.5dB and 1.5dB, if using one chip to drive the parallel load.
The treble is 92dB/W @ 1m.
1W into 6ohm is equivalent to 2.45V.
The sensitivity in volts is 92dB/2.45V @ 1m.
Rescale this for a 2.83Vac drive voltage and you get an extra 1.25dB.
The resulting voltage sensitivity is ~93.3dB/2.83V @ 1m.
Not quite the same as the woofer but pretty close. However, check the specifications of the drivers. Are the sensitivities quoted for 1W or 2.83V, it makes a difference.

Why limit your chipamps to 4ohm loading by paralleling the woofers? I would dedicate a chipamp to every driver. Now you can design for 6ohm loading and using a 24Vac transformer. If you use an active high pass filter as part of the treble crossover then you can probably get away with treating the treble driver as if it were an 8ohm load and go to a 25Vac or 26Vac transformer.

Finally, where are your speakers?
Are they spread around the room?
How do you intend to cable from a 10channel amplifier to all these distributed speakers/drivers.
Put each speaker amplifier right next to the speaker terminals. This remote amplifier can be a two channel or three channel device to suit the speaker it is driving. Speaker cables are very short. Speaker cable effect on amplifier stability is much reduced. Speaker cable cost is much reduced.
Line level twisted pair are much cheaper and much smaller to run to remote amplifiers.
__________________
regards Andrew T.

Last edited by AndrewT; 13th August 2010 at 10:41 AM.
  Reply With Quote
Old 14th August 2010, 12:12 AM   #559
niacinj is offline niacinj  United States
diyAudio Member
 
Join Date: Aug 2010
Thanks for the prompt response!
Ok, I've settled on the +-28vdc for both High and Low frequency amplifiers. I'm not too worried about matching the sensitivities because I can dial it in with the crossovers and an SPL meter.

You mentioned about having a separate amp for each woofer. Well, that would mean 15 amplifiers... A goal I'd like to work towards, but not yet. (Lack of funds...)
You also mentioned placing the amps near the speakers. I had looked into each speaker having a plate amp. Solen has a two-way plate amp with a built in crossover. I like the idea, but not enough to cut a big square out of the back of the speaker. I wouldn't have to use a plate for my design, though. However, I would need a 110 receptacle and a separate power transformer at each speaker. I'm fairly certain that my apartment has bad grounding, ground loops might be an issue. Speaker cable cost is greatly reduced, but now we need 5 transformers. I agree that this is the ideal solution, but not at the moment. With the modular format, these goals would be reached fairly easily down the road. (When there's more cash on hand )

For the time being, I would like to put the amplifiers in one case but I'm at a loss for what size transformer would be adequate to power all 10 amplifiers. Any ideas?
  Reply With Quote
Old 14th August 2010, 08:34 AM   #560
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
5 Mid/bass amplifiers and 5 Treble amplifiers from one transformer will never deliver 10*60W to your loads. Unless you were to accidentally send a Big DC pulse into the amps.

I assume the first amp needs 1.5*W as VA then the other 4 need 1*W as VA. Here I think it would be reasonable to assume that all 5 Treble amps need 0.5*W as VA.
That comes to a total of 480VA. That I reckon allows the amplifiers to think they are each being powered by a 90VA portion of the PSU. The range for economic transformers is 1 to 2times Watts for VA.
In this 10 amplifier case that becomes 320 to 640VA transformer.
You can use a 300VA transformer and the amps will perform pretty well. you can get small increases in performance as you move towards 600VA and not cost a lot of extra cash. Beyond 600VA the value for money in terms of performance per $ is going to get worse.

The amps will work with any 22+22Vac transformer between 200VA and 1000VA. You choose.
__________________
regards Andrew T.

Last edited by AndrewT; 14th August 2010 at 08:37 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
A Beginners Guide to Enclosure Alterations Bork Multi-Way 7 12th January 2009 02:10 AM
beginners ecl82 power supply emil_86 Tubes / Valves 15 25th September 2004 05:20 AM


New To Site? Need Help?

All times are GMT. The time now is 08:57 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2